1. Field of the Invention
The present invention relates to a process for efficient production of carboxylic acid esters and formamide by reacting carboxylic acid amides and formic acid esters, or by reacting carboxylic acid amides, alcohols, and carbon monoxide.
2. Description of the Related Arts
Carboxylic acid esters are industrially important compounds. As methods of producing carboxylic acid esters from carboxylic acid amides, (1) a method of producing methyl acetate from acetic acid amide, (2) a method of producing methyl methacrylate from methacrylic acid amide, (3) a method of producing methyl acrylate from acrylic acid amide, and (4) a method of producing methyl .alpha.-hydroxyisobutyrate from .alpha.-hydroxyisobutyric acid amide are known.
Formamide is used as a solvent, a treating agent, an electrolyte, or an antifreezing agent, or as an intermediate for production of dyes, pigments, medicines and so on. Moreover formamide is an important basic chemical compound which can be used also as a starting material for production of hydrogen cyanide.
For production of carboxylic acid esters from carboxylic acid amides, a method of reacting carboxylic acid amides and alcohols in the presence of sulfuric acid has heretofore been known, and this method is widely employed for industrial production of methyl methacrylate.
This method, however, has disadvantages in that a large amount of acidic ammonium sulfate results as a by-product, leading to a marked increase in production costs owing to its disposal, and an expensive corrosion-resistant apparatus is also required.
In order to overcome the above problems, a method of producing carboxylic acid esters by catalytic reaction of carboxylic acid amides and alcohols without sulfuric acid has been proposed.
This method, however, has disadvantages in that yield and selectivity of the desired carboxylic acid ester are low, a large amount of ammonia is formed and requires separation and recovery, and an ammonium salt of carboxylic acid is also formed. Thus the method is not satisfactory in commercial practice thereof.
As a method not accompanied by formation of ammonia, Japanese Patent Application Laid-Open Nos. 55444/1983 and 78937/1985 disclose a method of producing carboxylic acid ester and formamide by reacting carboxylic acid amide and formic acid ester in the presence of a catalyst comprising an organic or inorganic acid metal salt, or a metal carbonyl compound, and a nitrogen or phosphorus-containing organic compound.
These methods, however, have problems that the catalyst system is complicated and expensive, and catalyst recovery costs are high.